Mujaddara with Garlic Yogurt

What it is

Whole green or brown lentils, simmered until nearly soft, then finished with long-grain rice in the wide pan where four big onions have been browning slowly in olive oil. Two-thirds of the onions wait on a plate and go back on top at the end, sweet and deep brown. On the side, a cold garlic yogurt with lemon and dried mint.

It's the third of twenty Protein Champions, each recipe built around a different plant protein. And yes, rice again, like Champion number one. That's on purpose: in USDA FoodData Central's records, lentil protein carries more lysine and rice protein more of the sulfur pair, and a team in Toronto tested one side of that trade, rice's methionine joining lentils, in real people. You'll meet them in case one.

The lentils cook in plain water, no stock, and the yogurt is the only dairy: lacto-vegetarian all the way through. Four plates, so call someone over, or keep two for tomorrow's lunch. With rice in the pot, leftovers keep a day (see Storage).

Why you should eat it

The short version, before the onions go in. USDA FoodData Central lists 9.02 g of protein per 100 g of cooked lentils, with 7.9 g of fiber and 20.1 g of carbohydrate in that same 100 g, and barely any fat, 0.38 g. Lentil protein is rich in lysine and lighter on the sulfur pair (methionine and cysteine), while rice runs the other way, so each tops up the other. The garlic yogurt pulls its weight too: USDA lists 9.95 g of protein per 100 g of plain lowfat Greek yogurt. The four big onions bring fiber of their own, 1.7 g per 100 g raw (USDA), which my sums put at about a quarter of this plate's fiber. The lentils bring almost no sodium (USDA lists 2 mg per 100 g cooked), so the teaspoon of salt is the dial in your hand.

Tips

• Onions set the pace. Medium-low and patience: crank the heat and the edges burn before the middles turn sweet. That slow brown is the whole personality of this dish.
• Salt waits until the lentils have softened: Lentils.org says to season after cooking, because salt added before makes them tough. Here the teaspoon goes in once the lentils are soft outside and only a little firm in the middle. That halfway point is my call, not theirs.
• Lentils new to your plate? Going slow is allowed. In case four's 12-week trial, 87.7% of all gut-symptom ratings, lentil and poultry groups together, were none or mild, and the lentil eaters reported no more trouble than the poultry eaters. My suggestion, not the trial's: start with a smaller plate.

Substitutions

• Long-grain white rice: Coarse bulgur USDA's cooked bulgur record (170287) carries 3.86 g of the sulfur pair per 100 g of protein, a little under rice's 4.39, so the trade still works on paper. No study here tested lentils with bulgur. Follow the packet for liquid and time. The card is built on rice, so it won't match.
• Plain Greek yogurt, lowfat: Plain whole-milk yogurt, gelatin-free (check the label) Thinner, closer to a pouring sauce. USDA lists 3.47 g of protein per 100 g of plain whole-milk yogurt (171284) against 9.95 g for the lowfat Greek (170903), so the plate loses protein. The card is built on the Greek yogurt.
• Green or brown lentils: Split red lentils Not for this dish. Split red lentils cook in about 5 to 7 minutes (Lentils.org) and turn soft, so you'd lose the separate grains this recipe is built on. Save them for a soup.

Storage

The rice is in the pot, so the rice rule runs the whole dish: chill leftovers fast, ideally within an hour, keep them in the fridge no more than a day, and reheat them only once, until steaming hot all the way through (UK Food Standards Agency).

While it simmers: why the rice is in the pot

Lentils simmering, onions going slow, and thirteen minutes with only stirring to do. Pull up a chair.

Protein is a chain of amino acids, and your body strings each chain to a pattern, like a bead necklace with a fixed order of colors. Run out of one color and the necklace stops. The spare beads of every other color can't wait around, so they get burned for fuel.

Now the colors in this pan. In USDA FoodData Central's records, lysine makes up 6.98 g of every 100 g of protein in cooked lentils and 3.61 g in cooked white rice. The sulfur pair goes the other way: 4.39 g per 100 g of protein in the rice, 2.16 g in the lentils. Each carries plenty of the color the other is light on.

Here's the clever part. You can't watch a necklace being strung inside a person, but you can catch the burned beads on their breath. The Toronto team in case one did exactly that: more burning meant a color was running short. They added rice to lentils, and at the highest amount they tested, the burning dropped.

The lentils still do most of the work here: cooked, they carry about 3.4 times the protein of cooked rice (9.02 g against 2.69 g per 100 g, USDA). Run the raw records at this recipe's weights and the rice lifts the sulfur pair from 2.16 to 2.48 g per 100 g of protein, while lysine stays high at 6.51.

The picture stops in two places. The breath test reads protein building across the whole body, so it can't tell you what happened in your legs after squats. And in the lab every amino acid except methionine was topped up, so only one color could run short. A real plate is never that tidy.

So, in one line: lentils bring the lysine, rice brings more of the sulfur pair, and in five men in Toronto the body noticed, at the top amount tested.

Case one: five men, lentils, rice and a breath test

Researchers in Toronto took on this series' favourite question: put lentils and rice together, and does the body use more of the protein? Seven healthy young men signed up and five finished. Each was tested at 8 or 10 intakes of methionine, the sulfur amino acid lentils run lighter on.

It's the breath test from the necklace. Every other amino acid was topped up, so methionine was the only color that could run short, and a labelled phenylalanine showed on their breath how much was burned instead of built.

First finding: only 69% of the methionine in cooked lentils reached protein building. Then rice joined the same lentils. Overall, burning fell more steeply with rice in the mix, but level by level only the highest intake showed a clear difference: 16.2% less burned (P = 0.014). The lower two showed none, which the authors call surprising and can't explain.

On paper they went further: a protein score (DIAAS) of 91% for lentils in older children, teens and adults, and 143% for a 1:1 mix of lentils and rice. That 1:1 is arithmetic; the diet they fed mixed them at 2.93 to 1.

For your plate: in real people, rice's methionine helped cover what the lentils were short on, clearly so at the top intake. This pan makes the same pairing.

Where it stops: five men is tiny. The test reads whole-body protein building, not muscle, and cysteine, the other half of the sulfur pair, wasn't measured. The lentils were unsoaked and slow-cooked for 3 hours, and the authors say tannins, maybe the cooking too, could explain the fairly low 69%. A George Weston Ltd grant paid for it, and the authors report no conflicts. I'd love to see it repeated.

Case two: half the rice's carbs swapped for lentils

Healthy adults in Guelph, Canada, aged 18 to 40: 24 finished the rice part of this trial, 9 men and 15 women. On separate mornings each ate a meal carrying the same 50 g of available carbohydrate: white rice alone, or rice with half that carbohydrate swapped for large green, small green or split red lentils. Finger-prick blood sugar was checked for two hours.

Every lentil meal averaged a gentler rise than rice alone: 21.5% smaller with small green lentils and 20.5% with split red, both clear results, and 13.5% with large green, just short of the usual cut-off (P = 0.057). The peak fell from 7.8 mmol/L to between 6.9 and 7.1. Insulin didn't change.

For your plate: lentils supply roughly half this recipe's available carbohydrate, about 54% by my estimate, so it sits close to their test meal, though they cooked the two apart.

Where it stops: one meal per condition, in healthy young adults who knew what they were eating, on a meter the authors say isn't the gold standard. The lentil meals also carried more protein and fiber (18.2 g and 8.2 g with large green lentils, against 4.4 g and 0.9 g for rice), so the swap changed more than the carbs. Agriculture and Agri-Food Canada and a Pulse Canada program funded it, Pulse Canada and Alliance Grain Traders supplied the lentils, and the authors report no conflicts. If you manage your blood sugar, take this to your doctor before you change your plate around it.

Case three: lentil chili against rice chili

Twenty-four healthy adults in Guelph, 12 men and 12 women, average age 26. At three visits a week or more apart, each ate a chili: one with rice, two with the rice replaced by small green or split red lentils. The bowls matched for volume, and the rice chili carried at least as much energy. Then three hours of appetite ratings, an all-you-want pizza meal and a food record for the rest of the day.

Green lentils won the feelings round: fullness 17.5% higher over the three hours, desire to eat 20.1% lower, average appetite score 38.7% lower than after rice. Red lentils didn't separate from rice. Then the pizza: 801 kcal eaten after green lentils, 840 after red, 865 after rice, too close for the statistics to call (P = 0.12). The whole day matched too.

And one score I'm enjoying. Lentils have a reputation as the dutiful option, yet both lentil chilies beat the rice chili on taste, 68 against 54 on a 100 mm scale. Dutiful, apparently, can be delicious.

For your plate: in these adults, green lentils in place of rice brought three hours of feeling fuller, and the same amount eaten afterwards. Feeling full and eating less turned out to be two different results.

Where it stops: one meal each, in young, healthy, normal-weight adults, unblinded (you can see a lentil). Appetite was self-rated, and the authors note that the better-liked lentil chilies may have helped. A muffin version found no differences. Agriculture and Agri-Food Canada and a Pulse Canada program funded it, and the authors report no conflicts.

Case four: lentils at lunch for twelve weeks

In Montana, adults got seven prepared midday meals a week for 12 weeks. Thirty-eight finished, 35 women and 3 men, average age 47, all with a large waist and high blood fats after a fatty meal, signs of raised metabolic risk. Vegetarians were excluded. One group's meals carried 140 g of cooked whole green lentils a day, about 0.7 cup; the other group got ground turkey or chicken instead, with protein and energy matched.

Total cholesterol fell 0.11 mmol/L with lentils and rose 0.36 with poultry. Read the LDL slowly. The title says daily lentils improve fasting cholesterol, and the gap between the groups passed the statistics test (p = 0.02), but the lentil group's LDL barely moved: down 0.03 mmol/L, about 1.2 mg/dL. Most of the gap was the poultry group's LDL rising 0.30 (about 11.6 mg/dL). HDL, the one you usually want higher, slipped 0.07 with lentils and rose with poultry. After a fatty test meal, the blood sugar response fell in the lentil group. Weight and waist held steady.

For your plate: one plate of this recipe carries about 164 g of cooked lentils by my rough count, a little over their daily 140 g.

Where it stops: the groups didn't start level. The lentil group began with higher cholesterol, and more of the poultry group had metabolic syndrome (61% against 20%). Nobody was formally blinded, and the lentil meals also had more fiber and carbohydrate and less fat. The USDA's Pulse Crop Health Initiative funded it, AGT Foods Canada supplied the lentils, and the authors report no conflicts. If you're managing cholesterol, your doctor is the right person to read your numbers.